The present invention relates to motion compensation for a multiple reference frame architecture, and more particularly, to methods and apparatus for storing decoded moving pictures with a reduced memory requirement in contrast to the related art.
Regarding a multiple reference frame architecture (for example, an apparatus complying with H.264 specifications), some problems such as complicated memory access behavior and a high memory access rate of a main memory are introduced while multi-frame motion compensation is employed, where the main memory can be a dynamic random access memory (DRAM) accessed by a processor of the apparatus. Typically, the processor and the main memory are respectively positioned in different chips within the apparatus, so the memory bandwidth of the main memory may be insufficient due to complicated memory access behavior and/or high memory access rate required by a multiple reference frame architecture.
According to the related art, some suggestions with regard to a reduction of the corresponding memory requirement (e.g. the memory requirement of the DRAM) are proposed in order to solve at least a portion of the problems mentioned above. One suggests scaling decoded pictures, however, the picture quality is usually degraded with down-scaling. Another suggestion is compressing decoded pictures in a simpler way without randomly accessing a macroblock (MB). According to this suggestion, however, it is also very hard to prevent the picture quality from being degraded. According to another suggestion, just-in-time decoding of specific frames may be applied. However, the corresponding computation load is extremely heavy to cost-efficient hardware architecture.
As mentioned, the overall performance of an architecture implemented with at least one of the aforementioned suggestions is typically degraded due to some native characteristics of the multi-frame motion compensation. For example, referring to a situation shown in FIG. 1, reference data of a MB may be derived from multiple frames. In addition, more motion vectors and more intra information are involved in contrast to single frame motion compensation. Additionally, some issues related to long-term memory management might be encountered. Thus, according to the related art, even though the goal of reducing the corresponding memory requirement may be achieved, it is hard to prevent from introducing unwanted side effects.